Digest: darker section rule before 'From what you follow'

Per user — a heavier, darker divider (2px #9aa6b2) marks the brief→personal
section change, distinct from the light #e8e3d8 item separators above.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/digest.py

@@ -169,8 +169,11 @@ def build_digest(items: list[dict], brief_date: str, unsub_url: str, base: str |
     followed_html = ""
     if followed:
         followed_html = (
+            # A darker, heavier rule marks the section change (the item separators
+            # above are a light #e8e3d8) — a clear shift from brief to personal picks.
+            '<div style="border-top:2px solid #9aa6b2;margin:2px 0 22px"></div>'
             '<div style="font-size:20px;font-weight:700;letter-spacing:-0.01em;color:#0083ad;'
-            'margin:10px 0 28px">From what you follow</div>'
+            'margin:0 0 28px">From what you follow</div>'
             + "".join(_item_html(it, base) for it in followed)
         )
     html = (